1. Field of the Invention
The present invention relates to an automatic deceleration control method and apparatus for automatically decelerating a turning vehicle, thereby stabilizing the turning behavior of the vehicle.
2. Description of Related Art
In relation to stabilization of the turning behavior of a vehicle, Japanese Provisional Patent Publication No. 4-232349 discloses an output control apparatus for controlling engine output torque depending on road surface conditions. This apparatus sets the stability factor of the vehicle in accordance with an estimated road friction coefficient while the vehicle is turning. Based on the stability factor and detected vehicle speed and front-wheel steering angle, the apparatus computes an allowable lateral acceleration, and controls the output torque of the vehicle such that the allowable lateral acceleration is not exceeded. According to this output control apparatus, the output torque of the turning vehicle can be restricted depending on the road surface conditions, so as to prevent the vehicle from drifting out or spinning.
The allowable lateral acceleration computed by the conventional output control apparatus described above naturally takes a large value when the vehicle runs on a road surface with a relatively high friction coefficient. In the case of a passenger car which has a relatively low center of gravity, even if the allowable lateral acceleration takes a large value, the car body can be restrained from rolling by restricting an actual lateral acceleration applied to the body to the allowable lateral acceleration or below. However, a large-sized vehicle having a high center of gravity may fail to enjoy a stable turning behavior when undesired excessive rolling of the vehicle body occurs. Since the allowable lateral acceleration can be large in magnitude, such excessive rolling can occur, even if the actual lateral acceleration is restricted to the allowable lateral acceleration.